The invention pertains to a linear gas burner for the heat treatment of webs of material, especially for machines for flame lamination, with an elongated hollow body, closed at both ends, which has a feed line for fuel gas and a series of burner nozzles in one of its long sides, this hollow body being subdivided in the longitudinal direction by a baffle into a low-pressure space and a high-pressure space, into which at least one feed line for the fuel gas opens, the baffle for the fuel gas being provided with openings, which lead to the low-pressure space located between the baffle and the burner nozzles.
U.S. Pat. No. 366,780 describes a rectangular design, which consists of three parts, namely, a nearly flat base plate with a gas connection in the middle; a baffle in the form of an inverted pan with an arc-shaped, upward-curving yoke and two flat sidepieces in the form of segments of a circle, which diverge in the transverse direction as they extend downward; and a 3-dimensional nozzle body arranged above for producing the flame, which has approximately the form of half a hollow cylinder, closed at the ends, the entire extent of which is provided with burner nozzles in the surface of the half-cylinder. The nozzles are oriented in the radial direction, from which the flames also emerge in the radial direction. In a burner of this type, parts of different length must be fabricated for each different length of burner. This increases the cost of production.
In addition, the flames spread out widely, in all directions, which means that it is impossible to generate a directional effect, that is, to produce parallel flames with a strictly linear energy concentration. The heating of webs of material is not mentioned. When used for such a purpose, the wide energy distribution would lead to considerable energy losses and thus to poor efficiency; in addition, the area surrounding the burner would be heated up significantly, as a result of which the personnel operating the machine would be subjected to considerable stress. A burner of this type is not designed for heating in a linear fashion in its longitudinal direction and is thus neither intended nor suitable for heating a continuously traveling web of material uniformly across its width. Burners of this type are used primarily in cooking ovens, to heat rooms, and in open grate fireplaces.
DE 19 91 513 U describes a round burner for the combustion of gas-air feed mixtures, in which one or more perforated disks with holes offset with respect to each other and the burner nozzles are provided between a gas inlet and a nozzle plate. As a result, expansion and mixing chambers for the mixture are formed, and also the gas velocity is reduced. Although the round burner, in contrast to U.S. Pat. No. 366,780, has a strong directional effect, it is precisely for this reason that, because of its focused effect, it is unsuitable for uniformly heating wide, continuously traveling webs of material, nor is it intended for this purpose. It would merely produce strip-like burns in the traveling webs.
DE 39 16 142 A1 describes a linear or bar burner intended to heat sectional boilers for water heating, to which a gas-primary air mixture is supplied and to which, to reduce the formation of nitrous oxide, cooled secondary air is supplied to an area above the bases of the flames. A flat or curved burner plate is used. The secondary air guides are hollow, and cooling water flows through them; thus the secondary air is conducted across the outer surface of the secondary air guides by corresponding profiling to the core of the flame. In a preferred embodiment, the bar burner is arranged inside a trough, the side walls of which are provided with coolant channels parallel to the bar. The burner plate, however, is not preceded by any baffles or perforated structures for equalizing the flow and mixing the gas. The individual parts of the burner, including the nozzle plate, should preferably be made of profiled sheet steel, these sheet metal parts being welded together along their longitudinal edges. The possibility of the linear heating of traveling webs of material is not discussed.
Linear burners for the flame lamination of traveling webs of material are described in the prospectus for flame lamination machines of Schmitt-Maschinen. The hollow, elongated body is assembled from individual castings with graduated lengths of 20-40 cm. The butt joints between them, where the seals are located, must be machined, and the individual castings are screwed together in each case by four screws. The nuts or cap nuts are housed in pocket-like recesses, which constrict the inside cross section of the hollow body. Not only is it an extremely complicated matter to produce such burners, but the known linear burners also tend to become distorted under the effect of nonuniform temperature stresses.
It is also known that the hollow bodies of linear burners of this type can be assembled from two extruded half-shells, which, after assembly, have the form of a "U" in cross section. Seals and a row of screws are required at the joints between the shells, which again leads to the distortion of the linear burner or to deflection because linear burners of this type are subjected to the heat of the flame on only one side. It must be remembered that linear burners of this type can easily be anywhere from 2 to 4 meters long.
Common to all the known linear burners for flame lamination is that they do not have any effective devices in their interior by means of which the energy distribution of the flames in the longitudinal direction of the linear burner can be improved to a sufficient degree. As a rule, linear burners of this type are connected at both ends to fuel gas lines, through which a stoichiometric mixture of a gaseous hydrocarbon and an oxidation gas such as air is supplied. Because of the linear momentum of the flow of fuel gas, the pattern of the flame in the longitudinal direction of the linear burner is characterized by the absence of any flame at all at the two ends over a distance of about 15-25 cm. In the middle of the linear burner, furthermore, where the flows of gas from the two ends collide, the intensity of the flame produced is intensified. Although this is difficult to see from the length of the flame, it is very easy to verify on the basis of the end product.
Linear burners of this type are used for the flame lamination of webs of material. "Flame lamination" is a method for producing a composite of two or three material components (either single or sandwich lamination) on a calendering machine by exploiting the adhesive properties of foam when it is treated by the flame of a linear burner. Flame-laminating machines are used to bond thermoplastic materials such as foam sheets of polyester, polyether, or polyethylene or some other type of adhesive sheet to textiles, PVC sheets, artificial leather, nonwovens, papers, or other materials to produce, for example, covering materials for motor vehicle seats, articles of clothing, etc. A linear burner set up over the entire working width melts the surface of the foam sheet, as a result of which an adhesive film is formed. In the calender the foam sheet and the upper or lower layer are bonded together as they pass through a roll gap, a process which can be referred to as "bonding". The working speeds in this case depend on the material and can be as high as 60 m per minute.
The above-described nonuniform distribution of the burner energy now has the result that the terminal sections of the linear burner, which are about 15-25 cm long, are useless for the flame lamination process. As a result, the burners and thus the machine stand must be made longer than they would other wise have to be, which leads to a considerable increase in cost. But even so, the disadvantage remains that the greater flame intensity in the middle of the linear burner cannot be equalized. Considerable problems are therefore encountered in the regulation of the linear burner. The tolerance range within which the energy input can be adjusted is thus significantly restricted.
Against this background, the task of the invention is to improve a burner of the general type indicated above in such a way that it can be produced in virtually any length without having to arrange housing components next to each other in a row; is easy to install; and ensures a very uniform energy distribution over its entire length for the uniform heating of wide, traveling, temperature-sensitive webs of material, so that there is no longer any need to make the burner longer than it would otherwise have to be to accommodate the areas free of flame or with reduced heating output at the ends and so that the intensity peaks in the middle of the linear burner are avoided.